Steering and drive assembly for self-propelled units

ABSTRACT

A combination pump and motor assembly is operative connected to each of the two drive wheels. The pump and motor assemblies are controlled in the forward mode by a single speed lever. A steering wheel operates a rack and pinion assembly having two racks each of which is operatively connected to one of the pump and motor assemblies so that turning the steering wheel speeds up one pump and motor assembly and hence one drive wheel and slows up the other pump and motor assembly and hence the other drive wheel. Means are provided to over-ride the steering mechanism so that one pump and motor assembly or the other can be reversed thus allowing very sharp turns.

United States Patent 1 1 Pakosh 1 1 Jan. 23, 1973 [541 STEERING ANDDRIVE ASSEMBLY 3,61 1,827 10 1971 1361mm et al. ..l80/6.48 x FORSELF-PROPELLEI) UNITS 2,529,489 ll/l950 Curtis ..l80/6.2 X

[75] Inventor: Peter Pakosh, Winnipeg, Manitoba, Primary Examiner LeonFriaglia Canada Assistant Examiner-Leslie J. Paperner [73] Assignee:Versatile Manufacturing Ltd., AttorneyKent & Ade

Winnipeg, Manitoba, Canada 221 Filed: Feb. 8, 1971 1 ABSTRACT [21] ApplNo; 113,574 A combination pump and motor assembly is operative connectedto each of the two drive wheels. The pump and motor assemblies arecontrolled in the forward U-S- mode a ingle peed lever A steering wheel[51] Int. Cl. ..B62d 11/04 operates a ra k and pinion assembly havingtwo racks Field of Search 77 each of which is operatively connected toone of the 91, 2, 96 pump and motor assemblies so that turning thesteering wheel speeds up one pump and motor assembly [56] ReferencesCited and hence one drive wheel and slows up the other pump and motorassembly and hence the other drive UNITED STATES PATENTS wheel. Meansare provided to over-ride the steering 3,459,273 8/1969 Leinhauser..l80/6.48 mechanism that one P ami motor assembly of 2,882,753 4/1959Pakosh ....l80/6.2X other can be reversed thus allowing y Sharp2,941,609 6/1960 Bowers et al... ..l80/6.48 turns- 3,224,196 12/1965Bennett ..l80/6.48 x 3,581,497 6/1971 Krumholz ..l80/6.48 x 22 DrawmgFlgures PATENTEBJAK23I9T3 3,712,403

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STEERING AND DRIVE ASSEMBLY FOR SELF- PROPELLED UNITS This inventionrelates to new and useful improvements in self-propelled units,particularly self-propelled units which utilize a pump and motorassembly for driving for each of the drive wheels.

Although it is designed primarily for use with selfpropelled farmmachinery such as a self-propelled swather or a self-propelled combine,nevertheless it is readily adapted for use with other self-propelledvehicles and it is to be understood that the'claims of this applicationdo not limit the applicability of the invention to other forms ofimplements or vehicles.

Normally, self-propelled vehicles such as selfpropelled swathers and thelike are operated by a source of power through a system of belts,pulleys, gears and chains or chains or a combination of these, to thedrive wheels one upon each side of the vehicle or implement.

Steering is accomplished either by a pair of levers operating throughsplit pulley assemblies or, under certain circumstances, by a steeringwheel and column also operating split pulley assemblies.

However, due to the advent of hydraulic pump and motor assemblies,steering and reversing presents certain problems and the principalobject of this invention is to overcome these problems and provide aselfpropelled unit which can be steered by a steering wheel operatingthrough the pump and motor assemblies. Furthermore, means are providedto over-ride these steering assemblies in the event that it is necessaryto reverse one drive wheel. This is often required when harvesting andit is desired to make a square" comer or a right-angled turn in aminimum of space.

Another object of the invention is to provide a device of the characterherewithin described which includes means to center the steering wheeland to place both pump and motor assemblies in neutral when the singlespeed lever is moved to the neutral position.

Another object of the invention is to provide a device of the characterherewithin described in which a' single speed lever controls the forwardspeed of the unit from a neutral position to full forward speed, thesteering wheel operating the pump and motor assemblies regardless of theforward speed at which they are set.

A yet further object of the invention is to provide a A device of thecharacter herewithin described in which the riding reverse leveroperates the pump and motor assemblies regardless of the position of thespeed lever.

Another object of the invention is to provide a device of the characterherewithin described which enables smooth and easy steering to beaccomplished in such a unit as is described and yet at the same timepermits the steering assembly to be over-ridden in the event that asharp turn is required under which circumstances one drive wheel rotatesforward and the other rotates rearwardly.

With the considerations and inventive objects herein set forth in view,and such other of further purposes, advantages or novel features as maybecome apparent from consideration of this disclosure and specification,the present invention consists of the inventive concept which iscomprised, embodied, embraced or included in the method, process,construction, compoisition, arrangement or combination of parts, or newuse of any of the foregoing, herein exemplified in one or more specificembodiments of such concept, reference being had to the accompanyingFigures in which:

FIG. 1 is a side view of a self-propelled swather.

FIG. 2 is a top plan view.

FIG. 3 is a top plan view partially schematic of the drive connectionsto the ground wheels and the like.

FIG. 4 is a top plan view of the steering and drive control mechanism.

FIG. 5 is a side view of FIG. 4.

FIG. 6 is a top plan view of the rack and pinion assembly of thesteering device.

FIG. 7 is a side view of FIG. 6.

FIG. 8 is a view similar to FIG. 6, but showing the assembly in adifi'erent position.

FIG. 9 is an elevation of FIG. 6.

FIG. 10 is an enlarged plan view partially sectioned of the reverse andover-ride mechanism.

' In the drawings like characters of reference indicate correspondingparts in the different figures.

Proceeding therefore to describe the invention in detail, reference toFIGS. 1 and 2 will show a selfpropelled swather in general outline,including a frame generally designated 10 having a pair of front groundengaging drive wheels 11A and 1 18.

At the rear end 12 of the frame, a ground engaging castoring wheelassembly collectively designated 13, is mounted within a verticalbearing sleeve 13' and includes the fork l4 and the ground engagingwheel 15.

The frame 10 generally includes a pair of spaced and parallel sidegirder members 16 and atransverse front beam 17. The side member 17inclines inwardly and rearwardly as shown at 16A towards the'rear end ofthe other side frame member 16 and at the junction of these two members,the aforementioned castoring wheel assembly 13 is mounted.

A source of power in the form of a diesel engine or thelike is shown byreference character 18 and this is mounted towards the rear of theframe. A driver's position is indicated generally by reference character19 forwardly of the source of power and includes the enclosure 20 accessto which is reached by steps 21 in th usual manner.

Situated within the enclosure is a steering assembly collectivelydesignated 22, a speed lever 23 and a pair of reversing levers 24A and24B.

. Reference to FIG. 3 will show a main drive shaft assembly 25 and thisassembly is connected to the source of power 18 in the usual way, but itis not believed necessary to show details.

Belt pulleys 26 and 27 are mounted upon drive shaft 25 and drive belts26A extend around pulley 26 and around a further pulley 28. I

Similar belts 27A extend around pulley 27 and a further pulley 29.

V Pulleys 28 and 29 are mounted upon the drive shaft 30 of combinationpump and motor Zassemblies collectively designated 31 and 32 mountedupon frame members 33 which in turn extend between the front beam 17 anda cross beam 34 as clearly shown in FIG. 3.

These pump and motor assemblies are conventional and power from theengine 18 drives the pump portions 31A and 32A which in turn operate thehydraulic motor portions 313 and 323 respectively.

Pulleys 35 are driven by the output shafts 36 of the motors 31B and 32Band drive belts 37 extend around the pulleys and around further pulleys38 mounted upon shafts 39 which inturn are supported within bearingscarried by brackets 40 asclearly shown in FIG. 3. I

Chain and sprocket assemblies collectively designated 41 connect shafts39 to the aforementioned drivewheels 11A and 11B in the usual manner andas such construction is well known, it is not believed necessary to gointo details of this particular portion of the assembly.

The speed of the pump and motor assemblies 31 and 32 are controlledinternally in a conventional manner by rotation of control shafts 42Aand 428 which in turn are operated by speed control levers or cranks 43Aand 438 respectively.

Means are provided to operate these speed control levers 43A and 438from the aforementioned steering assembly 22 and in this connectionreference should be made to FIGS. 4 and 5.

An upwardly extending support component 44 is secured by the basethereof within the enclosure 20 and a steering column 45 is supportedwithin this support. A steering wheel 46 is secured to the upper end ofthe steering column and this column is pivotally supported at the upperend of the support component 44 by means of a ball joint bearingassembly 47 which permits the steering wheel 46 to be tilted fore andaft as will hereinafter be described.

Adjacent the lower end of the steering column, a universal joint 47 isprovided and a relatively short rod portion 48 of the steering columnextends from the universal joint downwardly therefrom.

A casing collectively designated 49 includes a hub 50 within which theaforementioned lower portion 48 is bearably supported and below this hubis substantially rectangular block or plate 51. A pinion 52 is securedto the lower end of the portion 48 of the steering column and issituated below the upper plate 57 of the casing and a pair of spaced andparallel rack bars 53A and 53B engage the pinion 52 one upon each sidethereof.

Recessed portions 54 are formed upon the underside of the upper plate 57and the rack bars run within these recessed portions being held inposition by means of a lower plate 58 spanning the underside of thecasing and being secured thereto by means of nut and bolt assemblies 59.This permits the rack bars to be moved longitudinally and in oppositedirections to one another, by rotation of the steering column 45, due tothe engagement of the pinion 52 with the two rack bars as clearly shownin FIGS. 6, 7, 8 and 9.

The casing itself, generally designated 49, is in turn supported forlongitudinal movement within limits and in thisconnection, alongitudinally extending groove 60 is formed upon each side of the upperplate portion 57. These grooves engage flanges 61 of spaced and parallelchannels 62 which in turn are secured to a pair of Iongitudinallyextending spaced and parallel frame members 63.

Link rods 64A and 64B are each pivotally secured by one end thereof asindicated by general reference character 65A and 658, to intermediatethe ends of links 66A and 66B, details of which will hereinafter bedescribed.

The other ends of the link rods 64A and 64B are connected by anadjustable ball joint component 67A and 678, to the ends of theaforementioned speed control levers 43A and 438 respectively.

The aforementioned links 66A and 66B are pivotted by the lower endsthereof to a shaft 68 which in turn is mounted between pairs of lugs 69secured to the front beam assembly 17.

An adjustable connecting link 70A and 70B is pivotally secured by oneend thereof to the upper ends of links 66A and 66B respectively and by aball joint 71A and 718, to adjacent one end of the aforementioned. rackbars 53A and 538 respectively, details being shown in FIG. 5.

From the foregoing it will be appreciated that rotation of the steeringwheel, which moves the two rack bars 53A and 538 in opposite directions,will also move the link rods 64A and 648 in opposite directions thusoperating the control shafts 42A and 42B of the pump and motorassemblies 31 and 32. It will also be apparent that due to the oppositemovement of the link rods 64A and 64B, one pump and motor assembly willbe speeded up and the other will have its speed reduced so that a turnwill be initiated with the faster ground engaging wheel rotating aroundslower wheel.

As an example, rotation of the steering wheel in the direction of arrow70 (FIG. 4) will cause link rods 648 to move in the direction of arrow71 thus rotating control shaft 428 in the direction of arrow 72 andslowing down the pump and motor assembly 32.

At the same time, link rods 64A will move in the 0pposite direction ofarrow 71 and rotate the control shaft 42A in the opposite direction thusspeeding up the pump and motor assembly 31, it being understood that therespective ground wheels are also slowed down and speeded uprespectively.

The forward speed of the vehicle or unit is controlled by the speedlever 23 which is mounted by the lower end thereof upon a shaft 73joumalled within bushings 74 supported within the aforementioned framemembers 63.

A quadrant plate 75 is secured to a vertical bracket 76 and thisquadrant'plate is provided with a plurality of apertures or depressions77 as shown in FIG. 5.

A springloaded pin assembly 78 extends through the lever 23 and engageswithin any one of the apertures or depressions 77 so that the lever 23does not move from the set position until it is desired to change thespeed.

Also mounted upon the cross shaft 73 is a pair of lugs or links 79 andadjustable yoke link 80 is pivotally secured by one end-thereof betweenthese links or lugs 79. The other end of this yoke link is in turnpivotally secured by means of a yoke 81, intermediate the ends of asingle link82. This link in turn is pivotally secured by the lower endthereof to a pivot 83 supported by the front beam 17 as shown in FIG. 5.

A relatively small link 84 is pivotally secured by one end thereof tothe upper end of the single link 82 and by the other end thereof to thehub 50 as shown in FIG. 7.

Therefore movement of the speed lever 23 from the position shown in FIG.5, in the direction of arrow 85, will move the casing 49 together withboth rack bars 53A and B, in the direction of arrow 71 (see FIG. 5).This in turn will cause both links bars 64A and B also to move in thedirection of arrow 71 thus rotating the control rods 42A and B in thedirection of arrow 72 thus in creasing the speed on both drive wheelsequally. Regardless of the final position of the speed control 23, thesteering can be controlled by the steering wheel 46 operating the tworack bars in opposite directions as hereinbefore described.

Due to the movement of the entire rack bar assembly together with thepinion and casing 49, it will be appreciated that the pinion will bemoved longitudinally also thus causing the steering column 45 to pivotaround its upper pivot 47 thus causing the steering wheel to tiltforwardly or rearwardly as hereinbefore described.

Under normal circumstances, the steering wheel will control the steeringcharacteristics of the unit satisfactorily.

However, when the unit is a self-propelled swather, for example, it isoften desirable that an extremely sharp turn be made when harvesting afield in order to form what is known as a square corner.

Under these circumstances it is necessaryto actually reverse themovement of drive wheel while maintaining the forward motion of theopposite drive wheel and in this connection means are provided tooverride the steering wheel control of the link rods 64A and B.

However, prior to describing this portion of the invention, mentionshould be made of the stop 86 which consists of a strip or bar extendingbetween the channel members 63 in alignment with the rack bars 53A andB. This stop is positioned so that when the speed lever 23 is in theneutral position shown in FIG. 5, the ends 87A and B of the rack bars53A and B, respectively, strike this stop.

lf-the steering wheel is turned when the speed lever 23 is moved to theneutral position, one rack bar 53A or B will strike the stop first andfurther movement of the speed control lever towards the neutral positionwill cause the pinion to rotate thus bring the other rack bar intocontact with the stop 86 and centering the steering wheel 46 and it willbe observed that the steering wheel cannot be turned when the speedcontrol lever is in the neutral position.

FIG. 8 shows the position of the rack bars when the speed control leveris advanced from the neutral position and the ends of the rack bars areaway from the stop so that they can be operated independently and inopposite directions by means of the steering wheel 46 as hereinbeforedescribed.

Referring back to the means to override the steering control the linkrods 64A and B, reference should be made to the aforementioned reversinglevers 24A and B. Each of these levers extends upwardly adjacent to thesteering wheel 46 and includes a bifurcated lower end 87A and B, saidbifurcated lower ends extending around the rods 64A and B respectively.The lower extremities of the bifurcated portions are pivoted to a crossbar or tube 88 which in turn is supported within brackets 89 secured toframe members 33.

Referring back to the pivotal connection 65A and 658 between the ends ofthe control rods 64A and B to the links 66A and B, reference to FIG.will show that a relatively short rod 89 slidably engages within the endof the rods 64A and B which takes the form of a tube. A first pivot pin90 extends through the links 65A and B and through a ball joint 91,links 66A and B consisting of two plates one upon each side of the balljoint 91.

It should be observed that the ends of this first pivot pin extendbeyond the links 66A and B.

A second pivot pin 92 extends through the rods 64A and B between theends thereof and through vertical slots 93 fom'ied in the bifurcatedends 87A and B of the reverse levers. Once again it should be noted thatthe extremities of this pivot pin 92 extend beyond the bifurcated sidesof the reverse levers.

Tension springs 93' extend between the extremities of pivot pin 90 andpivot pin 92 engaging within grooves 94 formed on the extendingextremities of these pivot pins.

From the foregoing it will be appreciated that when the link rods 64Aand B are actuated by means of the links 66A and B (that is by theoperation of the steering wheel 46) the tension of springs 93 transfersthe motion from the links 66A and B directly to the rods 64A and B.

However, when it is desired to override the steering and to reverse oneof the pump and motor assemblies, the relevant reversing lever 24A and Bis moved in the direction of arrow 95 or rearwardly. This causes thebifurcated portion of the reversing lever to move the link rod due tothe engagement of the second pivot pin 92 therewith, overriding thetension of springs 93' and extending same so that the end of the linkrods 64A and B slides away from the relatively short rod 89.

This causes the control rod 42A and B of the pump and motor assembly tomove in the opposite direction thus causing the relevant pump to reverseand to reverse the motion of the drive wheel driven thereby.

As soon as the reverse lever is released, the tension springs 93 returnit to the original position.

It will be observed that these reversing levers override the steeringmechanism regardless of the position of the speed lever 23 so that suchturns can be made at any speed desired.

Once this type of turn is completed, of course, the steering wheel 46once again becomes operative and steering can proceed in the usualmanner as hereinbefore described.

Finally reference should be made to FIG. 4 in which an alternativemounting for the springs 93' is shown in phantom. A brace 96 extendsacrossthe frame and a bracket 97 is clamped to the rod 648. Tensionsprings 98 extend between bracket 97 and fixed brace 96 and bias the rod64B towards shaft 68.

Several advantages flow from this construction including the fact thatall linkage play in the system is taken up by the springs 98, yet theystill operate in a manner similar to springs 93'. Furthermore thepositions of the springs in this location give feel or presence to thesteering wheel.

Various modifications can be made within the scope of the inventiveconcept which is herein disclosed and/or claimed.

What I claim as my invention is:

1. In a self-propelled unit including a frame, a source of power in saidframe, at least two ground engaging drive wheels joumaled one upon eachside of said frame, and a pair of combination pump and motor assembliesmounted in said frame, one being operatively connected to one drivewheel and the other being operatively connected to the other drivewheel, and speed control means on each of said pump and motorassemblies, the improvement which consists of a steering component and aspeed lever, both mounted in said frame, linkage means extending betweensaid steering component and the speed control means of each of said pumpand motor assemblies, whereby when one pump and motor assembly increasesin speed, the other pump and motor assembly decreases in speed andvice-versa, when said steering component is operated thus initiatingsteering movement to said unit, said steering component including apinion rotated by said steering component, a pair of longitudinallyextending rack bars one upon each side of said pinion and in spaced andparallel relationship with one another and engageable with said pinion,said linkage means being operatively connected between each rack bar andeach of said speed control means, means mounting said rack bars forlimited longitudinal sliding movement, and stop means engageable by oneend of each of said rack bars when said speed lever is moved to theneutral position thereby centering said steering component and movingsaid speed control means on both of said pump and motor assemblies, tothe neutral position.

2. The improvement according to claim 1 which includes a steering wheel,a steering column rotatable by said wheel, said pinion being mounted onthe lower end of said steering column.

3. The improvement according to claim 2 in which said means mountingsaid rack bars for limited longitudinal sliding movement includes acasing, a hub on said casing, the lower end of said steering columnbeing journaled for rotation in said hub, said pinion gear beingsituated in said casing, said rack gears being supported in said casingone upon each side of said pinion gear.

4. The improvement according to claim 3 in which said speed leverincludes means within which speed lever engages in a plurality ofincremental positions, linkage operatively extending between said speedlever and said casing mounting said rack gear and said pinions, andmeans on said frame mounting said casing for limited longitudinalsliding movement.

5. The improvement according to claim 4 in which steering column ispivoted adjacent the upper end thereof to said frame, and a universaljoint in said steering column adjacent the lower end thereof.

6. The improvement according to claim 5 which includes a reversing leverfor each of said pump and motor assemblies, each of said reversing leverincluding linkage means operatively connecting said reversing levers toone each of said pump and motor assemblies.

7. The improvement according to claim 6 which includes further means onsaid linkage means enabling said reversing levers to override said rackgears.

8. The improvement according to claim 7 in which each of said link rodsoperatively connected between said rack gears and said speed controlmeans includes a link pivotted by one end thereof to said frame and bythe other end thereof to adjacent one end of said rack bars, saidfurther means in said linkage means including a relatively short rodslidably engageable in one end of said link rod, a first pivot pinengaging through one end of said short rod and through said linkintermediate the ends of said link, the ends of said pivot pin extendingupon each side of said link, said reversing lever being pivotted by thelower end thereof to said frame, a

second pivot pin extending through said reversing lever and through saidlink rod, said second pivot pin extending upon each side of said linkrod and said reversing lever, and tension springs extending between theextending ends of said first pivot pin and the extending ends of saidsecond pivot pin.

9. The improvement according to claim 4 which includes a reversing leverfor each of said pump and motor assemblies, each of said reversinglevers including linkage means operatively connecting said reversinglevers to one each of said pump and motor assemblies.

10. The improvement according to claim 9 which includes further means onsaid linkage means enabling said reversing levers to override said rackgears.

l l. The improvement according to claim 10 in which each of said linkrods operatively connected between said rack gears and said speedcontrol means includes a link pivottedby one end thereof to said frameand by the other end thereof to adjacent one end of said rack bars, saidfurther means in said linkage means including a relatively short rodslidably engageable in one end of said link rod, a first pivot pinengaging through one end of said short rod and through said linkintermediate the extending upon of said link, the ends of said pivot pinextending upon each side of said link, said reversing lever beingpivottedby the lower end thereof to said frame, a second pivot pinextending through said reversing lever and through said link rod, saidsecond pivot pin extending upon each side of said link rod and saidreversing lever, and tension springs extending between the extendingends of said first pivot pin and the extending ends of said second pivotpin.

12. A self-propelled unit comprising in combination a frame, a source ofpower in said frame, a pair of ground engaging ground wheels one uponeach side of said frame and at one end thereof, a castoring wheelassembly supporting the other end of said frame, a pair of combinationpump and motor assemblies mounted in said frame, one for each drivewheel, said pumpand motor assemblies being operatively connected one toeach of said drive wheels, means operatively connecting said source ofpower to said pump and motor assemblies, speed control means on each ofsaid pump.

and motor assemblies, a steering component in said frame and a speedlever also mounted in said frame, whereby when one pump and motorassembly increases in speed, the other pump and motor assembly decreasesin speed and vice-versa, when said steering component is operated thusinitiating steering movement to said unit, said steering componentincluding a pinion rotated by said steering component, a pair oflongitudinally extending rack bars one upon each side of said pinion andin spaced and parallel relationship with one another and engageable withsaid pinion, a link rod operatively connected between each rack bar andeach of said speed control means, means mounting said rack bars forlimited longitudinal sliding movement, and stop means engageable by oneend of each of said rackbars when said speed lever is moved to theneutral position thereby centering said steering component and movingsaid speed control means on both of said pump and motor assemblies, tothe neutral position.

13. The improvement according to claim 12 which includes a steeringwheel, a steering column rotatable by said steering wheel, said pinionbeing mounted on the lower end of said steering column.

14. The improvement according to claim 13 in which said means mountingsaid rack bars for limited longitudinal sliding movement includes acasing, a hub on said casing, the lower end of said steering columnbeing journalled for rotation in said hub, said pinion gear beingsituated in said casing, said rack gears being supported in said casingone upon each side of said pinion gear.

15. The improvement according to claim 14 in which said speed leverincludes means within which speed lever engages in a plurality ofincremental positions, linkage operatively extending between said speedlever and said casing mounting said rack gear and said pinions, andmeans on said frame mounting said casing for limited longitudinalsliding movement.

16. The improvement according to claim 15 in which said steering columnis pivotted adjacent the upper end thereof to said frame, and auniversal joint in said steering column adjacent the lower end thereof.

17. The improvement according to claim .16 which includes a reversinglever for each of said pump and motor assemblies, each of said reversinglevers including linkage means operatively connecting said reversinglevers to one each of said pump and motor assemblies.

18. The improvement according to claim 17 which includes further meanson said linkage means enabling said reversing levers to override saidrack gears.

19. The improvement according to claim 18 in which each of said linkrods operatively connected between said rack gears and said speedcontrol means includes a link pivotted by one end thereof to said frameand by the other end thereof to adjacent one end of said rack bars, saidfurther means in said linkage means including a relatively short rodslidably engageable in one end of said link rod, a first pivot pinengaging through one end of said short rod and through said linkintermediate the ends of said link, the ends of said pivot pin extendingupon each side of said link, said reversing lever being pivotted by thelower end thereof to said frame, a second pivot pin extending throughsaid reversing lever and through said link rod, said second pivot pinextending upon each side of said link rod and said reversing lever, andtension springs extending between the extending ends of said first pivotpin and the extending ends of said second pivot pin.

20. The improvement according to claim 15 which includes a reversinglever for each of said pump and motor assemblies, each of said reversinglevers including linkage means operatively connecting said reversinglevers to one each of said pump and motor assemblies.

21. The improvement according to claim 20 which includes further meanson said linkage means enabling said reversing levers to override saidrack gears.

22. The improvement according to claim 21 in which each of said linkrods operatively connected between said rack gears and said speedcontrol means includes a link pivotted by one end thereof to said frameand by the other end thereof to adjacent one end of said rack bars saidfurther means in said linkage means includin a relatively short rodslidably engageable in one end 0 said link rod, a first pivot pinengaging through one end I of said short rod and through said linkintermediate the ends of said link, the ends of said pivot pin extendingupon each side of said link, said reversing lever being pivotted by thelower end thereof to said frame, a second pivot pin extending throughsaid reversing lever and through said link rod, said second pivot pinextending upon each side of said link rod and reversing lever, andtension springs extending between the extending ends of said first pivotpin and the extending ends of said second pivot pin.

1. In a self-propelled unit including a frame, a source of power in saidframe, at least two ground engaging drive wheels journaled one upon eachside of said frame, and a pair of combination pump and motor assembliesmounted in said frame, one being operatively connected to one drivewheel and the other being operatively connected to the other drivewheel, and speed control means on each of said pump and motorassemblies, the improvement which consists of a steering component and aspeed lever, both mounted in said frame, linkage means extending betweensaid steering component and the speed control means of each of said pumpand motor assemblies, whereby when one pump and motor assembly increasesin speed, the other pump and motor assembly decreases in speed andvice-versa, when said steering component is operated thus initiatingsteering movement to said unit, said steering component including apinion rotated by said steering component, a pair of longitudinallyextending rack bars one upon each side of said pinion and in spaced andparallel relationship with one another and engageable with said pinion,said linkage means being operatively connected between each rack bar andeach of said speed control means, means mounting said rack bars forlimited longitudinal sliding movement, and stop means engageable by oneend of each of said rack bars when said speed lever is moved to theneutral position thereby centering said steering component and movingsaid speed control means on both of said pump and motor assemblies, tothe neutral position.
 2. The improvement according to claim 1 whichincludes a steering wheel, a steering column rotatable by said wheel,said pinion being mounted on the lower end of said steering column. 3.The improvement according to claim 2 in which said means mounting saidrack bars for limited longitudinal sliding movement includes a casing, ahub on said casing, the lower end of said steering column beingjournaled for rotation in said hub, said pinion gear being situated insaid casing, said rack gears being supported in said casing one uponeach side of said pinion gear.
 4. The improvement according to claim 3in which said speed lever includes means within which speed leverengages in a plurality of incremental positions, linkage operativelyextending between said speed lever and said casing mounting said rackgear and said pinions, and means on said frame mounting said casing forlimited longitudinal sliding movement.
 5. The improvement according toclaim 4 in which steering column is pivoted adjacent the upper endthereof to said frame, and a universal joint in said steering columnadjacent the lower end thereof.
 6. The improvement according to claim 5which includes a reversing lever for each of said pump and motorassemblies, each of said reversing lever including linkage meansoperatively connecting said reversing levers to one each of said pumpand motor assemblies.
 7. The improvement according to claim 6 whichincludes further means on said linkage means enabling said reversinglevers to override said rack gears.
 8. The improvement according toclaim 7 in which each of said link rods operatively connected betweensaid rack gears and said speed control means includes a link pivotted byone end thereof to said frame and by the other end thereof to adjacentone end of said rack bars, said further means in said linkage meansiNcluding a relatively short rod slidably engageable in one end of saidlink rod, a first pivot pin engaging through one end of said short rodand through said link intermediate the ends of said link, the ends ofsaid pivot pin extending upon each side of said link, said reversinglever being pivotted by the lower end thereof to said frame, a secondpivot pin extending through said reversing lever and through said linkrod, said second pivot pin extending upon each side of said link rod andsaid reversing lever, and tension springs extending between theextending ends of said first pivot pin and the extending ends of saidsecond pivot pin.
 9. The improvement according to claim 4 which includesa reversing lever for each of said pump and motor assemblies, each ofsaid reversing levers including linkage means operatively connectingsaid reversing levers to one each of said pump and motor assemblies. 10.The improvement according to claim 9 which includes further means onsaid linkage means enabling said reversing levers to override said rackgears.
 11. The improvement according to claim 10 in which each of saidlink rods operatively connected between said rack gears and said speedcontrol means includes a link pivotted by one end thereof to said frameand by the other end thereof to adjacent one end of said rack bars, saidfurther means in said linkage means including a relatively short rodslidably engageable in one end of said link rod, a first pivot pinengaging through one end of said short rod and through said linkintermediate the extending upon of said link, the ends of said pivot pinextending upon each side of said link, said reversing lever beingpivotted by the lower end thereof to said frame, a second pivot pinextending through said reversing lever and through said link rod, saidsecond pivot pin extending upon each side of said link rod and saidreversing lever, and tension springs extending between the extendingends of said first pivot pin and the extending ends of said second pivotpin.
 12. A self-propelled unit comprising in combination a frame, asource of power in said frame, a pair of ground engaging ground wheelsone upon each side of said frame and at one end thereof, a castoringwheel assembly supporting the other end of said frame, a pair ofcombination pump and motor assemblies mounted in said frame, one foreach drive wheel, said pump and motor assemblies being operativelyconnected one to each of said drive wheels, means operatively connectingsaid source of power to said pump and motor assemblies, speed controlmeans on each of said pump and motor assemblies, a steering component insaid frame and a speed lever also mounted in said frame, whereby whenone pump and motor assembly increases in speed, the other pump and motorassembly decreases in speed and vice-versa, when said steering componentis operated thus initiating steering movement to said unit, saidsteering component including a pinion rotated by said steeringcomponent, a pair of longitudinally extending rack bars one upon eachside of said pinion and in spaced and parallel relationship with oneanother and engageable with said pinion, a link rod operativelyconnected between each rack bar and each of said speed control means,means mounting said rack bars for limited longitudinal sliding movement,and stop means engageable by one end of each of said rack bars when saidspeed lever is moved to the neutral position thereby centering saidsteering component and moving said speed control means on both of saidpump and motor assemblies, to the neutral position.
 13. The improvementaccording to claim 12 which includes a steering wheel, a steering columnrotatable by said steering wheel, said pinion being mounted on the lowerend of said steering column.
 14. The improvement according to claim 13in which said means mounting said rack bars for limited longitudinalsliding movement includes a casing, a hub on said casing, the lower endof said steering column being journalled foR rotation in said hub, saidpinion gear being situated in said casing, said rack gears beingsupported in said casing one upon each side of said pinion gear.
 15. Theimprovement according to claim 14 in which said speed lever includesmeans within which speed lever engages in a plurality of incrementalpositions, linkage operatively extending between said speed lever andsaid casing mounting said rack gear and said pinions, and means on saidframe mounting said casing for limited longitudinal sliding movement.16. The improvement according to claim 15 in which said steering columnis pivotted adjacent the upper end thereof to said frame, and auniversal joint in said steering column adjacent the lower end thereof.17. The improvement according to claim 16 which includes a reversinglever for each of said pump and motor assemblies, each of said reversinglevers including linkage means operatively connecting said reversinglevers to one each of said pump and motor assemblies.
 18. Theimprovement according to claim 17 which includes further means on saidlinkage means enabling said reversing levers to override said rackgears.
 19. The improvement according to claim 18 in which each of saidlink rods operatively connected between said rack gears and said speedcontrol means includes a link pivotted by one end thereof to said frameand by the other end thereof to adjacent one end of said rack bars, saidfurther means in said linkage means including a relatively short rodslidably engageable in one end of said link rod, a first pivot pinengaging through one end of said short rod and through said linkintermediate the ends of said link, the ends of said pivot pin extendingupon each side of said link, said reversing lever being pivotted by thelower end thereof to said frame, a second pivot pin extending throughsaid reversing lever and through said link rod, said second pivot pinextending upon each side of said link rod and said reversing lever, andtension springs extending between the extending ends of said first pivotpin and the extending ends of said second pivot pin.
 20. The improvementaccording to claim 15 which includes a reversing lever for each of saidpump and motor assemblies, each of said reversing levers includinglinkage means operatively connecting said reversing levers to one eachof said pump and motor assemblies.
 21. The improvement according toclaim 20 which includes further means on said linkage means enablingsaid reversing levers to override said rack gears.
 22. The improvementaccording to claim 21 in which each of said link rods operativelyconnected between said rack gears and said speed control means includesa link pivotted by one end thereof to said frame and by the other endthereof to adjacent one end of said rack bars, said further means insaid linkage means including a relatively short rod slidably engageablein one end of said link rod, a first pivot pin engaging through one endof said short rod and through said link intermediate the ends of saidlink, the ends of said pivot pin extending upon each side of said link,said reversing lever being pivotted by the lower end thereof to saidframe, a second pivot pin extending through said reversing lever andthrough said link rod, said second pivot pin extending upon each side ofsaid link rod and reversing lever, and tension springs extending betweenthe extending ends of said first pivot pin and the extending ends ofsaid second pivot pin.